1. Field of the Invention
The present invention relates to a printing apparatus for computer and the like, and more particularly to a printing apparatus utilizing an impact hammer as a printing means.
2. Description of the Prior Art
In printing apparatus utilizing a conventional ink roller, as shown in FIGS. 1 and 2, the printing operation of the hammer 3 is apt to cause the vibration of paper 4 in an extended area, thus eventually causing ink stain in other digit positions since the ink is applied by the ink roller 1 to the type faces of print drum 2. In order to prevent this drawback there is provided a stain preventing member 5 or 5', which is extended, as shown in the drawings, into all the spaces between two adjacent digits. In such arrangement, in order that the paper 4 is pushed beyond said stain preventing member 5, 5' to receive the ink from the print drum 2, the hammer 3 has to exert a strong pressure so as to bring said paper 4 into contact with the type face on the print drum 2, thus requiring an elevated level of printing energy and inevitably generating increased noise. Also the inevitable fluctuation in the distance from the stain preventing member 5, 5' to the surface of drum 2 has resulted in uneven print density for different digits or eventually in incomplete printing where a portion of a type face is not printable.
Such drawbacks are not solvable by merely improving the precision of the component parts, and have been a serious problem in maintaining the print quality particularly in consideration of the wear of the stain preventing member, drum, bearing etc. in the use.
In consideration of the drawbacks in the conventional apparatus, the present invention intends to provide a constant print quality even with a reduced print energy by maintaining constant the distance from the stain preventing member to the print drum.